What Causes the Speedometer to Fluctuate While Driving?
2 Answers
Reasons for speedometer fluctuations while driving: 1. Faulty charging circuit: If the battery cannot charge or is undercharged, the engine ECU will increase the engine speed to allow the alternator to charge the battery, causing the speedometer to fluctuate; 2. Faulty throttle: A malfunctioning throttle will alter the engine's air intake, leading to speedometer fluctuations; 3. PCV valve or carbon canister solenoid valve failure: When these valves malfunction, the fuel entering the combustion chamber will deviate from the ECU's settings, resulting in speedometer fluctuations; 4. Engine carbon buildup: Carbon deposits on the throttle can affect engine air intake, while combustion chamber carbon buildup can impact fuel injection and ignition, potentially causing pre-ignition or detonation, which makes the engine speed unstable.
I've experienced the issue of a fluctuating speedometer while driving, which is really annoying. Usually, it's caused by a faulty speed sensor. The sensor is located near the wheel and collects speed signals to transmit to the dashboard. Loose connectors or aging wiring can lead to unstable signals, causing the needle to jump up and down. Additionally, circuit problems in the dashboard itself can also cause this. Last time I checked, I found a blown fuse, and replacing it fixed the issue. A related point is that ignoring the problem could affect the ABS system or other safety functions, as misjudging speed while driving is dangerous. I recommend promptly visiting a professional repair shop to diagnose it with the right tools. Sometimes, simply cleaning the sensor interface can provide a temporary fix.
